Process for separating cobalt and nickel from ammoniacal solutions



United States Patent 3,107,996 PROCES FGR SEPARATEYG (IQBALT AND NECKEL FRQM AMMGNIACAL tlLUTiONS Ernst M. Gcltlstein, Newfield, NJ. No Drawing. Filed Sept. 19, 195i Ser. No. 56,678 1 Claim. (Cl. 75-103) This invention relates to the separation of nickel and cobalt from an ammoniacal solution in which they are dissolved and more particularly to a process in which the cobalt is selectively precipitated from the solution to provide eventually a nickel compound containing so little cobalt as to be commercially acceptable to a greater extent than heretofore.

A prior art process is known (Caron Patent 1,487,145) wherein nickel is extracted from nickeliferous ores containing some cobalt by reducing such ores in a furnace, next leaching the calcined ores in an ammoniacal solution to extract the nickel and the cobalt, and finally distilling the decanted product liquor to cause the nickel and cobalt to precipitate as nickel and cobalt compounds. In theory, such compounds will precipitate sequentially from the product liquor during distillation if most of the cobalt is in either the cobaltous or the cobaltic state and can be selectively filtered from the liquor. In actual practice, however, the two precipitates form practically simultaneously because of the presence in the product liquor of certain sulfur contaminants which tend so to affect the cobalt as to distribute it between the two states. It is therefore not commercially practical to separate the nickel and the cobalt by the known process so that after the intermixed nickel and cobalt compounds are calcined to form oxides of nickel and cobalt, the combined oxides, which are mainly nickel, are employed in industry wherever the amount of contained cobalt is not considered deleterious.

The foregoing inability to separate the cobalt from the nickel creates a number of disadvantages. Thus, if the amount of cobalt in the ore is so great that the finished oxides contain more than one part cobalt to one hundred parts nickel, the oxides have a considerably reduced market. To avoid this condition, it is customary to operate the process inefficiently in the leaching phase to limit the extraction of cobalt and thus produce a commercially acceptable product. However, this remedy has the effect of simultaneously lowering the amount of nickel eventually recovered leading to wastage of the nickel which ends up in the plant tailing heap.

The present invention contemplates a process in which the product liquor is treated with sodium formaldehydesul-foxylate (CH OH-O-SONa) as a reducing agent, thus converting most of the cobaltic compounds therein to the cobaltous form. The cobaltous compounds will precipitate upon distillation of the product liquor prior to any substantial precipitation of the nickel compounds thereby providing a means for selectively separating the cobalt and the nickel.

An object ot the present invention is to provide a process whereby cobalt is precipitated selectively from an ammoniacal solution containing nickel and cobalt by contacting such solution with a reducing agent before distillation of such solution.

Another object of the invention is the provision of a 3',l@'7,995 Patented Get. 22, 1963 process whereby cobalt is precipitated selectively from an ammoniacal solution containing nickel and cobalt by mixing therewith a chemical reducing agent before distillation of such solution.

A final object is to provide a process whereby cob-alt is precipitated selectively from an ammoniacal solution containing nickel and cobalt by mixing with the solution solid sodium :formaldehydesulfoxylate.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description.

The novel process disclosed herein is intended to be employed in conjunction with the well known Caron process mentioned heretofore for recovering nickel from nickel-i'ferous ore containing cobalt andiron such as is found in Cuba in considerable quantities The ore is dried to reduce substantially the moisture content, is ground to produce a finely divided mass, and is fed into the top of a vertical multiple hearth reduction furnace through which it passes downwardly at a slow rate. Undiluted producer :gas is introduced at a low point in the furnace and combustion gases may be introduced at various higher levels which cause the ore to be preheated to a temperature of about 600 C. and then to be slowly heated in a reducing atmosphere to a final temperature between 700 C. and 850 C.

The calcined ore is cooled after it leaves the furnace and is eventually treated with an ammoniacal solution of ammonium carbonate to leach out the nickel and cobalt. The ammoniacal solution is allowed to settle for a suflicient time to permit decantation of a product liquor containing a large percentage of the nickel in the ore and much of the cobalt. The product liquor is passed through a bubble tower countercurrent to a flow of steam which distills the ammonia and other dissolved gases such as carbon dioxide from the product liquor thereby causing the nickel and cobalt to precipitate generally in the form of carbonates. These carbonates may then be calcined to form oxides which are commercially useful. As previously pointed out, the nickel and cobalt co-precipitate and provide a final product which has more limited use than would a nickel product having a smaller cobalt content.

The present invention departs from the foregoing process by mixing the product liquor betore decantation and prior to distillation with sodium formaldehydesultoxylate which has the effect of causing reduction of substantially all of the cobaltic compounds to the cobaltous form in which form the cobalt will precipitate in the very early stages of distillation in advance of most of the nickel whereby the cobalt compounds may be separated selectively from the product liquor as by filtration or other separating methods. Very little of the nickel compounds will precipitate at this time so that it is possible to recover most of the nickel during subsequent distillation and relatively free of cobalt.

Example 1 in order to test the efiicacy of the foregoing reduction process, a number of product liquor samples containing varying amounts of cobalt with respect to the nickel content were treated with varying amounts of sodium formq? aldehydesulfoxylate. Thereafter, each product liquor was partially distilled until a fairly heavy precipitate appeared. The precipitate was separated from the remaining liquor and analyzed to determine what percentages of the nickel and cobalt originally in the product liquor were able further processing of the precipitate is necessary using conventional separation methods. As some of these methods work in ammoniacal solutions (e.g. the hydrogen reduction of nickel ahead of cobalt) and some 5 in acid medium (eg. the cobalt precipitation with hypoprecipitated From these figures, the parts cobalt to one chlorite solution) no limitations are encountered as to hundred parts nickel remaining in the filtrate were calcuthe preferred method because the precipitate can be dislated. The results of these tests are shown in the followsolved in acid and ammoniacal media and the solution ing table: is then ready for further processing.

Liquor compositions, g./l ml. Reducing agent Precip.

. Filtratc, pts. 00/ Ni 00 Pts. Col Cir/100 ml. G. per Percent Percent 100 pts. Ni

100 pts. Ni solution g. Co Ni Co 1. 21s 0. 0286 2. 35 0. 0657 2y 3 c. 4 70 0. 74

1. 212 0. 0286 2. as 0. 0657 2. a c. a 70. 7 0. 71

1. 212 0. 0286 2. 3s 0. 0s 2. s 9. o 69. 0 0. 7s

A study of the table shows that sodium formaldehyde- It will be apparent that a novel process has been desulfoxylate is particularly suitable for reducing the cobalt scribed whereby cobalt can be selectively precipitated from its cobaltic to the co'balbous form, in which form from an ammoniacal solution containing cobalt and it precipitates selectively from the product liquor after nickel. It should be understood, however, that the fore partial distillation thereof. Although some nickel is also going disclosure relates to only preferred embodiments precipitated, the remaining solution has considerably of the invention and that numerous modifications and fewer parts of cobalt to one hundred parts of nickel than alterations may be made therein without departing from did the original product liquor as a comparison of 001- the spirit and scope of the invention as set forth in the umns 3 and 8 will show. Column 8 also shows that 90 appended claim. when a sufiicient amount of the reducing agent is used, the o What is claimed and desired to be protected by Letter parts of cobalt to one hundred parts of nickel are brought Patent of the United States is: below the preferred commercial maximum of one. When In the recovery of nickel from an ammoniacal leach one considers that upon distillation of the untreated prodsolution containing ammonium carbonate, nickel, cobalt uct liquor, the cobalt and nickel are precipitated in suband the usual impurities, the process of obtaining'the stantially equal percentages so that there is no possibility nickel content substantially free of cobalt which comof achieving selective precipitation, the results produced prises mixing sodium formaldehydesulfoxylate with the by a simple treatment with this reducing agent seem quite solution, distilling the solution until a substantial amount remarkable. The precipitation with sodium formaldeof the cobalt in the solution in cobaltous form is selechydesulioxylate is preferably carried out in an oxygen- 40 tively precipitated, and separating the precipitate from the poor atmosphere. The precipitate obtained with sodium remaining solution. formaldehydesulfoxylate 1s soluble 1n ammoniacal solu- References (med in th6 file of this patent t10ns of ammonium carbonate as Well as 1n mineral acids such as sulfuric acid or hydrochloric acid. If the recov- UNETED STATES PATENTS cry of the small amount of co-precipi-tated nickel is desir- 2,913,336 Dean Nov. 17, '1959 

